software node: Handle software node injection to an existing device properly

The function software_node_notify() - the function that creates
and removes the symlinks between the node and the device - was
called unconditionally in device_add_software_node() and
device_remove_software_node(), but it needs to be called in
those functions only in the special case where the node is
added to a device that has already been registered.

This fixes NULL pointer dereference that happens if
device_remove_software_node() is used with device that was
never registered.

Fixes: b622b24519f5 ("software node: Allow node addition to already existing device")
Reported-and-tested-by: Dominik Brodowski <linux@dominikbrodowski.net>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

diff --git a/drivers/base/swnode.c b/drivers/base/swnode.c
index 3cc11b8..d1f1a82 100644 (file)
--- a/drivers/base/swnode.c
+++ b/drivers/base/swnode.c
@@ -1045,7 +1045,15 @@ int device_add_software_node(struct device *dev, const struct software_node *nod
        }
 
        set_secondary_fwnode(dev, &swnode->fwnode);
-       software_node_notify(dev, KOBJ_ADD);
+
+       /*
+        * If the device has been fully registered by the time this function is
+        * called, software_node_notify() must be called separately so that the
+        * symlinks get created and the reference count of the node is kept in
+        * balance.
+        */
+       if (device_is_registered(dev))
+               software_node_notify(dev, KOBJ_ADD);
 
        return 0;
 }
@@ -1065,7 +1073,8 @@ void device_remove_software_node(struct device *dev)
        if (!swnode)
                return;
 
-       software_node_notify(dev, KOBJ_REMOVE);
+       if (device_is_registered(dev))
+               software_node_notify(dev, KOBJ_REMOVE);
        set_secondary_fwnode(dev, NULL);
        kobject_put(&swnode->kobj);
 }
@@ -1119,8 +1128,7 @@ int software_node_notify(struct device *dev, unsigned long action)
 
        switch (action) {
        case KOBJ_ADD:
-               ret = sysfs_create_link_nowarn(&dev->kobj, &swnode->kobj,
-                                              "software_node");
+               ret = sysfs_create_link(&dev->kobj, &swnode->kobj, "software_node");
                if (ret)
                        break;